No registration or passwords; no pop-up ads -- just aloha, fun, & answers.
(as an eBay Partner & Amazon Affiliate earns from qualifying purchases).
Home /
T.O.C.
Fun
FAQs
Good
Books
Ref.
Libr.
Advertise
 
Help
Wanted
Current
Q&A's
Site 🔍
Search
pub  Where the
world gathers for metal finishing
Q&As since 1989



-----

Black oxide comes out red, need jet black finish




Q. What way is there to produce a deep jet black finish on steel other than black oxide. We are having parts coming out reddish in the black oxide. We need another process that comes out as black as black oxide.

Thanks,

Vero Dewis
- Florida




A. You don't say if you or an outside metal finisher is doing the black oxide process. Regardless, as the black oxide tank becomes aged, a build-up of iron occurs (from the steel). This is the red you see. Years ago, we could complex this to prevent it. The chemical was a carcinogen, don't think anyone uses it now. Best to contact the supplier of the black oxide salts, ask him what to do.

Black oxide is made up at 7 1/2 lbs./gal. of water, operates at 295 degrees F. Can be deadly if you do not have proper equipment and know-how to operate. There are cold blacks that are equivalent to hot black oxide. Suppliers support this web site. An alternative possibility is zinc electroplate followed by black chromate. More expensive. Really depends on what application the finished parts see.

Bill Hemp
tech svc. w/ chemical supplier - Grand Rapids, Michigan




A. I'm a big fan of black oxide, so maybe looking at bath maintenance would help solve your problem. That said, you could also look at black zinc phosphate. Phosphate will help hide some imperfections in the steel that black oxide would leave exposed. Hope this helps.

Dan Brewer
chemical process supplier - Gurnee, Illinois


A. Hi. If you are 100% sure that a process is properly controlled and it still doesn't give you what you are looking for, it's time to look for a replacement. But the fact that parts are coming out red isn't evidence that black oxiding isn't viable, but that you are not operating it correctly.

In addition to the points raised by Bill and Dan, a very simple concept that I didn't get until it was explained by Rod Henrickson (search our site for his name) is that the black oxide tank must be at a rolling boil and must also be at the right temperature. That is, you cannot control the temperature by modulating the heat input, you can only control it by modulating the water content. To be overly brief, Rod says red parts can indicate that the solution is not boiling or the temperature is too high, so you need to add water. Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 6, 2012




(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

 
Jobshops
Capital
Equipment
Chemicals &
Consumables
Consult'g, Train'g
& Software


About/Contact  -  Privacy Policy  -  ©1995-2024 finishing.com, Pine Beach, New Jersey, USA  -  about "affil links"